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When plasmas ten times hotter than the core of the Sun begin pulsating inside the °ÄÃÅÁùºÏ²Ê¸ßÊÖ vacuum vessel, the combined mass of the Tokamak and cryostat (25,000 tonnes) will need a bit of breathing space. Not much—but enough to accommodate the wobbling, expansions and occasional displacements caused by the tremendous forces at work in the machine. Anchored into the "crown," the circular arrangement of 18 spherical bearings will allow for the smooth transfer of horizontal and rotational forces, giving the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak the indispensable "room to breathe." In order to protect the installation and guarantee its safety, the Tokamak support system will need to be both extremely robust, with a strong connection to the Tokamak Complex basemat, and yet allow for a slight freedom of movement for the cryostat.   Connection and stability will be achieved by way of a massive pedestal—a concrete "crown," connected to walls that are radially anchored to the three-metre-thick bioshield. Eighteen radial walls will act as the flying buttresses of a medieval cathedral, providing an efficient and elegant solution for the even distribution of loads and efforts.   Movement will be permitted thanks to a circular arrangement of 18 spherical bearings that act like ball-and-socket joints and allow for the smooth transfer of horizontal and rotational forces, whether stemming from normal operations, a vertical displacement event or an earthquake.   Such a combination of strong support structure and sliding or spherical bearings is commonly used in large bridges.   However while the mechanical principles at work in the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak support system are the same, the materials implemented will need to be very different.   "In the ordinary world, the bearings would be coated in Teflon, the well-known polymer used in non-stick cookware", explains Robert Fielder, technical responsible officer for the system. "Teflon is very efficient in reducing friction between bearing and socket but unfortunately would not survive in the punishing environment of the Tokamak, where radiation at the base of the cryostat would soon cause it to lose its properties."   For the industrial contractor in charge of manufacturing the bearings (Nuvia, the company that also designed and installed the anti-seismic system of the Tokamak Complex), the challenge was to identify a material that could substitute for Teflon and offer a similar, or even better, low-friction coefficient.   The 1/2 scale prototype in the Nuvia test rig, equipped with thermal probes and optic and electric strain gauges. It took about six months of research and the testing of dozens of alloys, ceramics and compounds before settling on a copper-aluminium alloy that—combined with a micro lubricant (molybdenum sulphur)—would do the job to perfection. The combination already works for other °ÄÃÅÁùºÏ²Ê¸ßÊÖ systems, in some components of the Wendelstein stellarator, and in deep-space applications.   The design of the bearings is now finalized. Nuvia has produced and successfully tested scaled models (one-fourth and one-half of the actual size) and will now build a full-scale prototype along with a specific installation to host it, as no laboratory or testing facility in Europe can reproduce the monster loads to which the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak will be subjected.  

At China's Institute of Plasma Physics (ASIPP), activities to qualify the tooling and materials for the fabrication of °ÄÃÅÁùºÏ²Ê¸ßÊÖ's poloidal field magnet #6 (PF6) continue. This second-smallest ring magnet for °ÄÃÅÁùºÏ²Ê¸ßÊÖ will be fabricated in China on the basis of an agreement concluded with the European Domestic Agency.   In January, we reported on the successful trial activities for the winding tooling, as well as qualification steps for the vacuum chamber and welding and insulation procedures.   In the latest news, helium inlet welding was further trialled and tooling for de-spooling, for connecting lengths of conductor with their power feeders (dummy joint boxes), and for supporting the weight of the coil assembly during insulation and impregnation were tested. All of these qualification steps allow engineers to spot potential manufacturing problems and introduce improvements so that the final coils are in line with specification.   A four-day audit by the European Domestic Agency was also conducted on all processes, the handling of raw material, documentation and standards. Read the full story on the European Domestic Agency website.

  Click here for all °ÄÃÅÁùºÏ²Ê¸ßÊÖ photos. Like elements in a giant Erector Set, the four steel girders (each weighing 155 tonnes) and trolleys are now ready to be assembled into a double overhead crane capable of lifting the heaviest °ÄÃÅÁùºÏ²Ê¸ßÊÖ components.   Last week, a 10-axle, 80-wheel self-propelled vehicle transported the large and heavy elements from their temporary storage into the Assembly Hall.   Girders and trolleys will be lifted into position by a huge crawler crane operating from outside the 60-metre-tall building, which will pass its hook through an opening in the roof.   The first elements of the crawler crane, one of the tallest in the world, were delivered to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site on Monday 6 June; it will take more than 50 trucks to deliver them all and 10 days to finalize their assembly.   Click here for more photos of activity inside the Assembly Hall.

Ronald C. Davidson, a pioneering plasma physicist for 50 years who directed the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) during a crucial period of its history and was a founding director of the Plasma Fusion Center at the Massachusetts Institute of Technology (MIT), passed away on 19 May at his home in Cranbury, New Jersey. He was 74. "Ron was an anchor for the Laboratory both through his science and through his wisdom," said Stewart Prager, director of PPPL. "His prodigious contributions not just to PPPL's science but also to plasma physics writ large are clear and widely known. Within the Laboratory, he was a mentor and a guide to people young and old. His impact within the Laboratory was enormous." The physicist won numerous honours in his lifetime, including the prestigious James Clerk Maxwell Prize in Plasma Physics in 2008, the highest national honour in plasma physics. He was a fellow of both the American Physical Society and the American Association for the Advancement of Science. Davidson was known as a prolific researcher, writer and academic. Read the full-length obituary on the PPPL website.

On the last day of her state visit to France, South Korea's President Park Geun-hye stopped in Grenoble, a city in the French Alps where she studied in the mid-1970s after graduating from South Korea's Sogang University. Nostalgia wasn't the only reason for this last stop, however. The South Korean President wished to visit the Air Liquide plant in Sassenage, where hydrogen fuel cell vehicles are being developed in cooperation with the Korean automaker Hyundai Motor Co. Also of interest to President Park were the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cold boxes that are currently being equipped with internal components before integration into the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cryoplant. One of the three °ÄÃÅÁùºÏ²Ê¸ßÊÖ cold boxes (21 metres long, 4.2 metres in diameter) provided a spectacular background to the presentation of the company's activities by Xavier Vigor, Air Liquide advanced Technologies CEO. Also present were Benoît Potier, Air Liquide Chairman and Chief Executive Officer, and Pierre-Etienne Franc, Vice President of Advanced Business & Technologies. It was the second time the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cold boxes were in presidential company: in August 2015 French President Hollande also made a stop at the Air Liquide plant and even signed cryoplant cold box number two ... --Photo courtesy of Air Liquide Click here for an article in the Korea Times and here to watch a video on French public TV.

New computer simulations at the Princeton Plasma Physics Laboratory (PPPL) indicate that an innovate start-up technique for tokamaks, called coaxial helicity injection (CHI), may support a strong electric current without a traditional solenoid magnet. In tokamaks, a complex web of magnetic fields control the superhot plasma. In addition to large D-shaped magnets surrounding the vacuum vessel, a central electromagnet known as a solenoid participates in creating the twisting vortex that prevents the plasma from touching the tokamak's walls. Compact spherical tokamaks, like the NSTX-U recently dedicated at PPPL, as well as future tokamaks may not have room for solenoids. During CHI, magnetic field lines, or loops, are inserted into the tokamak's vessel through openings in the vessel floor. The field lines then expand to fill the vessel space, like a balloon inflating with air, until the loops undergo a process known as magnetic reconnection and snap closed. The newly formed closed field lines then induce current in the plasma. "Can we create and sustain a big enough magnetic bubble in a tokamak to support a strong electric current without a solenoid?" asks Physicist Fatima Ebrahimi, who performed the computer simulations. "The findings indicate that 'yes, we can do it.'" Read the full article on the PPPL website. --Image: Physicist Fatima Ebrahimi

In line with a First Plasma in 2017, the 41-tonne vacuum vessel of the MAST Upgrade project was returned to its concrete-shielded home in late May, where it can now be refitted with its components and systems before commissioning. The upgraded MAST tokamak will help to add to the knowledge base for °ÄÃÅÁùºÏ²Ê¸ßÊÖ by experimenting with key plasma physics issues. Watch a short video of the milestone on the website of the Culham Centre for Fusion Energy (UK).